Sealing devices in common use for sealing against fluid leakage between relatively moving machine elements have performance limitations and operational disadvantages. The elastomeric radial type lip seal utilizes an extremely narrow lip contact area and a tight fit around a shaft circumference in order to effectively seal. The seal pressure increases the tightness of the fit. The resulting high pressure loadings at the sealing surfaces prevents the formation of a lubricant film. High sealed pressures and sliding speeds are severely limited, as the sliding friction causes rapid destruction of the sealing surfaces. Mechanical axial flat face seals have relatively large sealing areas that effectively seal. However, the combination of the flat face and the large sealing area prevents the entrance of the sealed fluid between the sealing surfaces to form a lubricant film adequate for high sealed pressures and sliding speeds. The sliding friction generated by these operating conditions would destroy the sealing surfaces by wear and overheating. Low viscosity sealed fluids, such as water, are particularly deleterious to both the radial lip and axial face seals.
Open path labyrinth and externally pressurized sealing devices are used when the operating requirements are beyond the capability of sliding surface closed path seals. These seals also have performance limitations and disadvantages. The labyrinth seal requires an excessively long length to seal substantial pressures and is limited to applications where continuous leakage is acceptable and where a means for collecting and disposing of the leakage fluid is convenient and available. The externally pressurized sealing device blocks fluid leakage by admittance of a fluid pressurized by an external source into the leakage path. The pressurized fluid leaks both internally and externally. The fluid must be compatible with the system fluid and a means for disposing of the external leakage must be provided. The requirement for an external pressure source and the energy consumption are obviously undesirable.
What is needed is a closed path fluid seal that can operate over an unlimited range of sealed pressures, speeds, and sealed fluid viscosity. It is the object of this invention to provide such a fluid seal.